P1674: CLINICAL IMPACT OF NON-ADHERENCE TO HIT GUIDELINES: A DOUBLE HIT IN HIT
Authors: A. Al Raizah, A. Almozaini, R. Abu Eishah, K. Alharbi, M. almufarrih, M. Al Shuaibi, O. K. Alkhairy, M. Alzahrani, A. Hejazi, A. Alaskar
Journal: HemaSphere (2022)

Background: Heparin induced thrombocytopenia (HIT) is a pro-thrombotic complication of heparin. In patients with suspected HIT,guidelines recommend to use 4Ts score to estimate the probability of HIT and recommend against HIT testing in patients with a low probability. Use of this score would limit overtesting, unnecessary anticoagulation, bleeding, and thrombosis from holding heparin. In patients with an intermediate or high probability, guidelines recommend holding heparin and starting a non-heparin anticoagulant. Aims: Describe clinical management and consequences of non-adherence to HIT guidelines Methods: This is a retrospective study at single tertiary hospital. All inpatients 16 years or older who have been tested for HIT between june 2019 to end of june 2021 were included. Patintes were exculded if the reason for sending HIT was a repeat test. Data were collected retrospectively by manual chart review. HIT pretest probability was calculated using the 4Ts score by 2 independent hematologist. Any variations in 4Ts score were solved by discussion. Score of 0 to 3 considered low, 4-5 intermediate and 6-8 high probability. Outcomes: Low probability: 1. Frequency of requesting HIT test. 2. Thrombosis secondary to holding heparin defined as venous thrombosis (VTE) from time of holding heparin till death or 90 days after discharge. 3. Frequency of using alternative anticoagulant and consequent bleeding defined as bleeding from start of alternative anticoagulant till 24 hours after last dose. Moderate and high probability: 1. Frequency of not stopping heparin and starting alternative anticoagulant. 2. Thrombosis (VTE or arterial) in patients not started on alternative anticoagulant defined as thrombosis from sending HIT till 90 days after discharge or death. VTE included pulmonary embolism, deep vein thrombosis and thrombosis in unusual sites. Arterial events included cerebrovascular accidents, mesenteric, limb ischemia and myocardial infarction. HIT test was done using Stago Asserachrom HPIA‐IgGAM ELISA with level of < 0.4 considered negative. Informed consent was waived. Results: After exclusion of the repeat test (13), 302 patients were included in this study. Most common reason to request HIT test was low platlet 288 (95%). Most of the patients 183 (60.6 %) were low probability, 108 (35.8%) intermediate and the rest 11(3.6%) were high probability. In the low probability group,166(90.7%) of patients had negative HIT Eliza (Table 1 & 2). Management and outcome: Low probability (table 3): Heparin was stopped in 85(46.4 %). Three out of these patients developed thrombosis (3.5%). Alternative anticoagulant was started in 12(6.5 %) patients. Bleeding developed in 9(5%) patients none of these events were secondary to the alternative anticoagulant. Moderate and high probability (table 4): Heparin stopped in 60 patients (50.4%).Majority 95(79.8 %)were not started on alternative anticoagulant.Thirteen (13.6%) of these patients developed thrombosis. Image:Summary/Conclusion: We found that nonadherence to HIT guidelines is common and had a substantial impact. In the low probability group, overtesting for HIT is highly prevalent. This exposed patients to unnecessary anticoagulation. In the intermediate and high probability group, majority of patients were not started on alternative anticoagulant which may explain the high rate of thrombosis. Quality initiatives which incorporate education about evidence-based management of HIT, consistently applying these in practice, and incorporating them into electronic systems could minimize these consequences and lead to safer, more cost-effective care. Cuker, A, et al. Blood advances 2.22 (2018)